1. Field of the Invention
This invention relates to an automatic canceling device for a winker and, more particularly, to an automatic canceling device for a winker of electric type for unlocking by the attraction of a solenoid even if a winker operation knob is disposed at a position separate from a steering shaft.
2. Description of the Prior Art
In an automatic canceling device or an electric type winker of this type, a winker operation lever rotated by an operation knob is generally rockably provided in a case. A driving rod is slidably held through a compression spring at the lever, and pressed under pressure with an opposite cam. The cam has, as shown in FIGS. 6(a) and 6(b), a stationary cam unit 1, and an elevationally movable cam unit 3 disposed in a slit 2 formed at the center of the cam unit 1. Grooves 4 and 5 are respectively formed at the cam units 1 and 3 for holding the winker operation lever at its neutral position, and locking grooves 6 and 7 are formed at the cam unit 1 for holding the winker operation lever at the left and right positions. The movable cam unit 3 is urged downward by a spring, and unlocked, i.e., moved upward by a solenoid energized by an unlock signal, for example, due to the returning rotation of the steering wheel.
The operation of the automatic canceling device for the conventional winker constructed as described above will be described.
FIG. 6(a) shows a cam portion such that the winker operation lever is locked at left or right position. In the state shown in FIG. 6(a), the movable cam unit 3 is retracted so that the plane of the groove 5 is disposed at the same as the plane of the grooves 6 and 7 for locking the stationary cam unit 1, a driving rod of the winker operation lever is, though not shown, engaged with the groove 6 or 7, and the winker operation lever is locked at the left or right position. Thus, left or right winker is intermittently flashed.
When the steering wheel is rotatably returned, a switch is actuated by the cam of the steering shaft to energize the solenoid. The movable cam unit 3 is moved upward against a compression spring by the energization of the solenoid, and the plane of the groove 5 of the movable cam unit 3 is disposed in the same plane as that of the groove 4 of the stationary cam unit 1 as shown in FIG. 6(b). Then, the driving rod engaged with the groove 6 or 7 is moved to the ends 6a, 7a of the center side of the groove 6 or 7 while being pressed by the groove 5 of the movable cam unit 3, to ride over the ends 6a, 7a of the center side in the state as shown in FIG. 6(b) to be moved to and held in the grooves 4, 5 of neutral position. Then, the solenoid is deenergized, the movable cam unit 3 is moved down by the spring, and returned to the state as shown in FIG. 6(a). In this case, even if the groove 5 of the movable cam 3 is moved down to become the state not contacted with the driving rod, the driving rod is engaged with the groove 4 of the stationary cam unit 1, and the winker operation lever is held at its neutral position.
However, in the prior art described above, in order to dispose the winker operation lever at its neutral position without fluctuation, the compression spring for pressing the driving rod in contact with the groove 4 of the cam needs a spring tension of predetermined degree. Accordingly, when the driving rod is engaged with the left or light grooves 6 or 7, the spring tension further increases. Since the movable cam unit 3 is moved upward to press the driving rod against the compression spring by the energization of the solenoid in this state, the spring tension of the compression spring in case of unlocking is increased, a large solenoid is required to move upward the movable cam unit 3 against the spring tension which prevents the reduction in its size and enhance its cost.